DE-OSS 1,928,409 and 2,161,645 describe coatings of polymers of alkyl esters, hydroxyalkyl esters, methylol ethers of methacrylamide and, optionally, quaternary aminoalkyl esters of acrylic or methacrylic acid. However, the coatings are too sensitive to mechanical stressing and swell on wetting, so that they lose their adhesion to the substrate.
DE-PS 2,017,002 describes plastics containing small quantities of a surfactant, for example polyglycols. In this case, the effects obtained are too weak for practical application. The addition of the surfactant results in swelling of the plastic in water and, hence, in premature degradation on weathering.
U.S. Pat. No. 4,576,864 describes two-layer water-spreading coatings of which the lower layer is a hydrophobic polymer while the upper layer is formed from colloidal silica. The disadvantage of these coatings lies in the relatively complicated application of two layers which can be avoided by the coatings according to the present invention.
In addition, the coatings according to the present invention consist of thermoplastic material so that they may be applied by co-extrusion.
Finally, it is known from DE-OS 1,694,273 that the optical properties of thermoplastic moldings can be improved by coatings, the thermoplastic moldings consisting of polyacrylate or polycarbonate and the plastics suitable for coating consisting of polyacrylate or cellulose acetobutyrate for the polyacrylates and of polycarbonate, polyacrylate, cellulose acetobutyrate or polystyrene for the polycarbonates. The problem of spreading water is not discussed in DE-OS 1,694,273.
The segmented, aliphatic-aromatic polyether copolycarbonates are known (see, for example, DE-OS 2,251,066, U.S. Pat Nos. 4,160,791, 4,075,108, 4,069,151).
They may be obtained from diphenols H--D--OH (III), polyether diphenol carbonates ##STR1## and phosgene in known manner by the interfacial method (see, for example, DE-OS 3,408,804).